1. Field of the Invention
The present invention concerns a top-comb drive mechanism applied to a high speed comber and characterized by a very high number of nips of more than 250 to 350/minute.
2. Description of the Related Arts
To clarify the purpose of the present invention, first the problems of the high-speed comber for which a solution is required by the cotton spinning industry will be explained, and thereafter, the various technical advances that have been made in an effort to solve these problems will be described.
In the conventional combing machine, it is well known that the top comb is usually moved along an identical moving locus during the forward and rearward displacements thereof. In such a combing machine, to ensure a satisfactory combing action by the top comb, preferably the working time of the top comb is such that the combing action time is long enough that the combing action is started as early as possible during each cycle thereof. Nevertheless, if the starting time of the combing action of the top-comb is early, a top comb of the combing mechanism may work on a front edge portion of a fringe at which a unit combing action by a combing cylinder has been completed, in a condition such that the front edge portion of the combed fringe is not completely gripped by the detaching rollers, i.e., a timing just before the piecing operation of the forward edge portion of the combed fringe with the rearward edge portion of the fleece gripped by the detaching rollers is commenced. As the result of this action of the top-comb, fibers useful for producing a yarn may be removed as "waste fiber", and further, a folding of the front edge of fibers in the combed fringe may occur, which will cause an irregular piecing of the combed fringe with the rearward edge portion of the fleece gripped by the detaching rollers. To eliminate this drawback, if the starting time of the combing action by the top-comb is retarded, the working time of the combing action is shortened, and thus the combing action applied to the rearward portion of the fleece is not sufficient, i.e., short fibers and impurities in the fleece can not be completely removed, and accordingly, a desirable combing action by the top-comb can not be obtained.
To solve the above-mentioned problem, Japanese Examined Patent Publication No. 38-4715 (1963) discloses that the upwards and downwards motion of the top-comb be carried out by applying a locus of the forward and rearward displacing motions of the top-comb, wherein the locus of the forward displacing motion thereof is different from the locus of the rearward displacing motion thereof. According to this invention, the forward end portion of the combed fringe is gripped by the detaching rollers so that the combed fringe is displaced forward while providing a draft in the zone between the nip point of the detaching rollers and the nip point between the cushion plate and the feed roller, and the top-comb is rapidly inserted into the fleece to which the above-mentioned draft is applied. Accordingly, a forward displacement of the portion of the fleece upstream from the position at which the top-comb is inserted is disturbed, and accordingly, an irregular draft is created and a high speed drive of the combing machine can not be carried out.
In Japanese Unexamined Patent Publication No. 60-194125 (1985), the applicant of the present patent application proposed an improvement of the mechanism of the apparatus disclosed by the above-mentioned Japanese Examined Patent Publication No. 38-4715. In this apparatus, the top-comb is guided by a combined outside contacting cam surface formed by a movable cam and a stationary cam so that the top-comb is moved along a locus of a forward displacement thereof and a locus of a rearward displacement which is different from the locus of forward displacement, to eliminate the above-mentioned drawback of the apparatus disclosed by Japanese Examined Patent Publication No. 38-4715. This improved mechanism, however, has the following drawbacks, i.e., since in this apparatus, a cam ball is contacted from the outside of the guide-cam surface formed by the combination of two guide-cam surfaces wherein one surface thereof is the cam-surface of the movable cam, it is necessary to provide a detachable device for this movable cam, and thus it is impossible to drive the combing machine at a speed faster than 250 nips/minute. A very loud noise due to the displacing motion of the cam ball between the above-mentioned two cam surfaces also creates a problem in the working environment of spinning factories. Moreover, when the motion of top-comb must be adjusted to conform to changes of the raw material, etc., the adjustment must be applied to each combing head one by one, separately, and such an adjusting operation incurs a longer down time for maintenance of the combing machine concerned.